Sensor Inserter Assembly

ABSTRACT

An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte, such as blood glucose. An inserter having a retractable introducer is provided for subcutaneously implanting the sensor in a predictable and reliable fashion.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/538,067 filed Aug. 7, 2009, which is a continuation application ofU.S. patent application Ser. No. 11/899,917 filed Sep. 6, 2007, now U.S.Pat. No. 8,029,442, which is a continuation application of U.S. patentapplication Ser. No. 10/703,214 filed Nov. 5, 2003, now U.S. Pat. No.7,381,184, which claims priority based on U.S. Provisional ApplicationNo. 60/424,099, entitled “Sensor Inserter Device and Methods of Use,”filed on Nov. 5, 2002, the disclosures of each of which are incorporatedherein in their entirety by this reference.

BACKGROUND

The monitoring of the level of glucose or other analytes, such aslactate or oxygen, in certain individuals is vitally important to theirhealth. High or low levels of glucose or other analytes may havedetrimental effects. The monitoring of glucose is particularly importantto individuals with diabetes, as they must determine when insulin isneeded to reduce glucose levels in their bodies or when additionalglucose is needed to raise the level of glucose in their bodies.

A conventional technique used by many diabetics for personallymonitoring their blood glucose level includes the periodic drawing ofblood, the application of that blood to a test strip, and thedetermination of the blood glucose level using colorimetric,electrochemical, or photometric detection. This technique does notpermit continuous or automatic monitoring of glucose levels in the body,but typically must be performed manually on a periodic basis.Unfortunately, the consistency with which the level of glucose ischecked varies widely among individuals. Many diabetics find theperiodic testing inconvenient and they sometimes forget to test theirglucose level or do not have time for a proper test. In addition, someindividuals wish to avoid the pain associated with the test. Thesesituations may result in hyperglycemic or hypoglycemic episodes. An invivo glucose sensor that continuously or automatically monitors theindividual's glucose level would enable individuals to more easilymonitor their glucose, or other analyte, levels.

A variety of devices have been developed for continuous or automaticmonitoring of analytes, such as glucose, in the blood stream orinterstitial fluid. A number of these devices use electrochemicalsensors which are directly implanted into a blood vessel or in thesubcutaneous tissue of a patient. However, these devices are oftendifficult to reproducibly and inexpensively manufacture in largenumbers. In addition, these devices are typically large, bulky, and/orinflexible, and many cannot be used effectively outside of a controlledmedical facility, such as a hospital or a doctor's office, unless thepatient is restricted in his activities.

Some devices include a sensor guide which rests on or near the skin ofthe patient and may be attached to the patient to hold the sensor inplace. These sensor guides are typically bulky and do not allow forfreedom of movement. In addition, the sensor guides or the sensorsinclude cables or wires for connecting the sensor to other equipment todirect the signals from the sensors to an analyzer. The size of thesensor guides and presence of cables and wires hinders the convenientuse of these devices for everyday applications. The patient's comfortand the range of activities that can be performed while the sensor isimplanted are important considerations in designing extended-use sensorsfor continuous or automatic in vivo monitoring of the level of ananalyte, such as glucose. There is a need for a small, comfortabledevice which can continuously monitor the level of an analyte, such asglucose, while still permitting the patient to engage in normalactivities. Continuous and/or automatic monitoring of the analyte canprovide a warning to the patient when the level of the analyte is at ornear a threshold level. For example, if glucose is the analyte, then themonitoring device might be configured to warn the patient of current orimpending hyperglycemia or hypoglycemia. The patient can then takeappropriate actions.

SUMMARY

The present invention is, in general, directed to devices and methodsfor the in vivo monitoring of an analyte, such as glucose or lactate,using a sensor to provide information to a patient about the level ofthe analyte. More particularly, the present invention relates to devicesand methods for inserting a subcutaneously implantable electrochemicalsensor in a patient for such monitoring.

Generally, the present invention relates to methods and devices for thecontinuous and/or automatic in vivo monitoring of the level of ananalyte using a subcutaneously implantable sensor. Many of these devicesare small and comfortable when used, thereby allowing a wide range ofactivities. One embodiment includes a sensor control unit having ahousing adapted for placement on skin. The housing is also adapted toreceive a portion of an electrochemical sensor. The sensor control unitincludes two or more conductive contacts disposed on the housing andconfigured for coupling to two or more contact pads on the sensor. Atransmitter is disposed in the housing and coupled to the plurality ofconductive contacts for transmitting data obtained using the sensor. Thesensor control unit may also include a variety of optional components,such as, for example, adhesive for adhering to the skin, a mountingunit, a receiver, a processing circuit, a power supply (e.g., abattery), an alarm system, a data storage unit, a watchdog circuit, anda measurement circuit. The sensor itself has at least one workingelectrode and at least one contact pad coupled to the working electrodeor electrodes. The sensor may also include optional components, such as,for example, a counter electrode, a counter/reference electrode, areference electrode, and a temperature probe. The analyte monitoringsystem also includes a display unit that has a receiver for receivingdata from the sensor control unit and a display coupled to the receiverfor displaying an indication of the level of an analyte. The displayunit may optionally include a variety of components, such as, forexample, a transmitter, an analyzer, a data storage unit, a watchdogcircuit, an input device, a power supply, a clock, a lamp, a pager, atelephone interface, a computer interface, an alarm or alarm system, aradio, and a calibration unit. In addition, the analyte monitoringsystem or a component of the analyte monitoring system may optionallyinclude a processor capable of determining a drug or treatment protocoland/or a drug delivery system.

According to one aspect of the invention, an insertion kit is disclosedfor inserting an electrochemical sensor into a patient. The insertionkit includes an introducer. A portion of the introducer has a sharp,rigid, planar structure adapted to support the sensor during insertionof the electrochemical sensor. The insertion kit also includes aninsertion gun having a port configured to accept the electrochemicalsensor and the introducer. The insertion gun has a driving mechanism fordriving the introducer and electrochemical sensor into the patient, anda retraction mechanism for removing the introducer while leaving thesensor within the patient.

According to another aspect of the invention, a method of using anelectrochemical sensor is disclosed. A mounting unit is adhered to theskin of a patient. An insertion gun is aligned with a port on themounting unit. The electrochemical sensor is disposed within theinsertion gun and then the electrochemical sensor is inserted into theskin of the patient using the insertion gun. The insertion gun isremoved and a housing of the sensor control unit is mounted on themounting base. A plurality of conductive contacts disposed on thehousing is coupled to a plurality of contact pads disposed on theelectrochemical sensor to prepare the sensor for use.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The Figures and the detailed description which follow moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a block diagram of one embodiment of a subcutaneous analytemonitor using a subcutaneously implantable analyte sensor, according tothe invention.

FIG. 2 is a top view of one embodiment of an analyte sensor, accordingto the invention.

FIG. 3 is an expanded side view of one embodiment of a sensor and anintroducer, according to the invention.

FIGS. 4A, 4B, 4C are cross-sectional views of three embodiments of theintroducer of FIG. 3.

FIG. 5 is a cross-sectional view of one embodiment of an on-skin sensorcontrol unit, according to the invention.

FIG. 6 is a top view of a base of the on-skin sensor control unit ofFIG. 5.

FIG. 7 is a bottom view of a cover of the on-skin sensor control unit ofFIG. 5.

FIG. 8 is a perspective view of the on-skin sensor control unit of FIG.5 on the skin of a patient.

FIG. 9 is a perspective view of the internal structure of an insertiongun, according to the invention.

FIG. 10A is a top view of one embodiment of an on-skin sensor controlunit, according to the invention.

FIG. 10B is a top view of one embodiment of a mounting unit of theon-skin sensor control unit of FIG. 10A.

FIG. 11A is a top view of another embodiment of an on-skin sensorcontrol unit after insertion of an introducer and a sensor, according tothe invention.

FIG. 11B is a top view of one embodiment of a mounting unit of theon-skin sensor control unit of FIG. 11A.

FIG. 11C is a top view of one embodiment of a housing for at least aportion of the electronics of the on-skin sensor control unit of FIG.11A.

FIG. 11D is a bottom view of the housing of FIG. 11C.

FIG. 11E is a top view of the on-skin sensor control unit of FIG. 11Awith a cover of the housing removed.

FIG. 12 depicts an introducer, sensor, insertion gun and mounting unit,which can be assembled and sold together in an insertion kit.

FIG. 13 is a perspective view showing a preferred commercial embodimentof a sensor inserter and adhesive mount constructed according to theinvention.

FIG. 14 is a perspective view of the adhesive mount and sensor attachedto the patient's skin.

FIG. 15 is a perspective view of the transmitter attached to theadhesive mount.

FIG. 16 is an exploded perspective view of the preferred commercialembodiment of FIG. 13.

FIG. 17 is a side elevation view of the preferred commercial embodimentof FIG. 13.

FIG. 18 is an end elevation view of the preferred commercial embodimentof FIG. 13.

FIG. 19 is a cross-sectional view taken along line 19-19 in FIG. 18.

FIG. 20 is a cross-sectional view taken along line 20-20 in FIG. 17.

FIG. 21 is a broken away view similar to FIG. 20, showing the shuttle inthe neutral position.

FIG. 22 is a broken away view similar to FIG. 20, showing the shuttle inthe cocked position.

FIG. 23 is a broken away view similar to FIG. 20, showing the shuttle inthe insertion position.

FIG. 24 is a cross-sectional view taken along line 24-24 in FIG. 17.

FIG. 25 is a perspective view of a transcutaneously implantable sensor.

FIG. 26A is a perspective view of a sensor introducer.

FIG. 26B is a bottom view of the introducer shown in FIG. 26A.

FIG. 27 is a perspective view of a shuttle member.

FIG. 28 is a top plan view of an oversized adhesive tape.

FIG. 29 is a perspective view of the transmitter attached to theadhesive mount and showing the sensor sandwiched therebetween.

FIG. 30 is a perspective view of the interconnect on one end of thetransmitter.

FIG. 31 is an enlarged perspective view of the interconnect of FIG. 30with the seal and one spring removed for clarity.

FIG. 32 is an enlarged perspective view of the interconnect seal.

FIG. 33A is a perspective view of an alternative embodiment of a sensorinserter kit.

FIG. 33B is an exploded view of some of the components shown assembledin FIG. 33A.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

The present invention is applicable to an analyte monitoring systemusing an implantable sensor for the in vivo determination of aconcentration of an analyte, such as glucose or lactate, in a fluid. Thesensor can be, for example, subcutaneously implanted in a patient forthe continuous or periodic monitoring of an analyte in a patient'sinterstitial fluid. This can then be used to infer the glucose level inthe patient's bloodstream. Other in vivo analyte sensors can be made,according to the invention, for insertion into a vein, artery, or otherportion of the body containing fluid. The analyte monitoring system istypically configured for monitoring the level of the analyte over a timeperiod which may range from days to weeks or longer.

The analyte monitoring systems of the present invention can be utilizedunder a variety of conditions. The particular configuration of a sensorand other units used in the analyte monitoring system may depend on theuse for which the analyte monitoring system is intended and theconditions under which the analyte monitoring system will operate. Oneembodiment of the analyte monitoring system includes a sensor configuredfor implantation into a patient or user. For example, implantation ofthe sensor may be made in the arterial or venous systems for directtesting of analyte levels in blood. Alternatively, a sensor may beimplanted in the interstitial tissue for determining the analyte levelin interstitial fluid. This level may be correlated and/or converted toanalyte levels in blood or other fluids. The site and depth ofimplantation may affect the particular shape, components, andconfiguration of the sensor. Subcutaneous implantation may be preferred,in some cases, to limit the depth of implantation of the sensor. Sensorsmay also be implanted in other regions of the body to determine analytelevels in other fluids. Examples of suitable sensor for use in theanalyte monitoring systems of the invention are described in U.S. patentapplication Ser. No. 09/034,372 and Ser. No. 09/753,746 (the completeparent application to this CIP), both incorporated herein by reference.

One embodiment of the analyte monitoring system 40 for use with animplantable sensor 42, and particularly for use with a subcutaneouslyimplantable sensor, is illustrated in block diagram form in FIG. 1. Theanalyte monitoring system 40 includes, at minimum, a sensor 42, aportion of which is configured for implantation (e.g., subcutaneous,venous, or arterial implantation) into a patient, and a sensor controlunit 44. The sensor 42 is coupled to the sensor control unit 44 which istypically attached to the skin of a patient. The sensor control unit 44operates the sensor 42, including, for example, providing a voltageacross the electrodes of the sensor 42 and collecting signals from thesensor 42. The sensor control unit 44 may evaluate the signals from thesensor 42 and/or transmit the signals to one or more optionalreceiver/display units 46, 48 for evaluation. The sensor control unit 44and/or the receiver/display units 46, 48 may display or otherwisecommunicate the current level of the analyte. Furthermore, the sensorcontrol unit 44 and/or the receiver/display units 46, 48 may indicate tothe patient, via, for example, an audible, visual, or othersensory-stimulating alarm, when the level of the analyte is at or near athreshold level. In some embodiments, an electrical shock can bedelivered to the patient as a warning through one of the electrodes orthe optional temperature probe of the sensor. For example, if glucose ismonitored then an alarm may be used to alert the patient to ahypoglycemic or hyperglycemic glucose level and/or to impendinghypoglycemia or hyperglycemia.

A sensor 42 includes at least one working electrode 58 formed on asubstrate 50, as shown in FIG. 2. The sensor 42 may also include atleast one counter electrode 60 (or counter/reference electrode) and/orat least one reference electrode 62. The substrate 50 of the sensor maybe formed using a variety of non-conducting materials, including, forexample, polymeric or plastic materials and ceramic materials. Suitablematerials for a particular sensor 42 may be determined, at least inpart, based on the desired use of the sensor 42 and properties of thematerials.

In some embodiments, the substrate is flexible. For example, if thesensor 42 is configured for implantation into a patient, then the sensor42 may be made flexible (although rigid sensors may also be used forimplantable sensors) to reduce pain to the patient and damage to thetissue caused by the implantation of and/or the wearing of the sensor42. A flexible substrate 50 often increases the patient's comfort andallows a wider range of activities. Suitable materials for a flexiblesubstrate 50 include, for example, non-conducting plastic or polymericmaterials and other non-conducting, flexible, deformable materials.Examples of useful plastic or polymeric materials include thermoplasticssuch as polycarbonates, polyesters (e.g., Mylar™ and polyethyleneterephthalate (PET)), polyvinyl chloride (PVC), polyurethanes,polyethers, polyamides, polyimides, or copolymers of thesethermoplastics, such as PETG (glycol-modified polyethyleneterephthalate).

In other embodiments, the sensor 42 is made using a relatively rigidsubstrate 50 to, for example, provide structural support against bendingor breaking Examples of rigid materials that may be used as thesubstrate 50 include poorly conducting ceramics, such as aluminum oxideand silicon dioxide. One advantage of an implantable sensor 42 having arigid substrate is that the sensor 42 may have a sharp point and/or asharp edge to aid in implantation of a sensor 42 without an additionalintroducer.

It will be appreciated that for many sensors 42 and sensor applications,both rigid and flexible sensors will operate adequately. The flexibilityof the sensor 42 may also be controlled and varied along a continuum bychanging, for example, the composition and/or thickness of the substrate50.

In addition to considerations regarding flexibility, it is oftendesirable that implantable sensors 42 should have a substrate 50 whichis non-toxic. Preferably, the substrate 50 is approved by one or moreappropriate governmental agencies or private groups for in vivo use.

Although the substrate 50 in at least some embodiments has uniformdimensions along the entire length 57 of the sensor 42, in otherembodiments, the substrate 50 has a distal end 67 and a proximal end 65with different widths 53, 55, respectively, as illustrated in FIG. 2. Inthese embodiments, the distal end 67 of the substrate 50 may have arelatively narrow width 53. For sensors 42 which are implantable intothe subcutaneous tissue or another portion of a patient's body, thenarrow width 53 of the distal end 67 of the substrate 50 may facilitatethe implantation of the sensor 42. Often, the narrower the width of thesensor 42, the less pain the patient will feel during implantation ofthe sensor and afterwards. The sensor 42 is designed to be a replaceablecomponent in an implantable analyte monitor. Typically, the sensor 42 iscapable of operation over a period of days. Preferably, the period ofoperation is at least three days. The sensor 42 can then be removed andreplaced with a new sensor.

An introducer 120 can be used to subcutaneously insert the sensor 42into the patient, as illustrated in FIG. 3. The introducer 120 istypically formed using structurally rigid materials, such as metal orrigid plastic. Preferred materials include stainless steel and ABS(acrylonitrile-butadiene-styrene) plastic. In some embodiments, theintroducer 120 is pointed and/or sharp at the tip 121 to facilitatepenetration of the skin of the patient. A sharp, thin introducer mayreduce pain felt by the patient upon insertion of the sensor 42. Inother embodiments, the tip 121 of the introducer 120 has other shapes,including a blunt or flat shape. These embodiments may be particularlyuseful when the introducer 120 does not penetrate the skin but ratherserves as a structural support for the sensor 42 as the sensor 42 ispushed into the skin.

The introducer 120 may have a variety of cross-sectional shapes, asshown in FIGS. 4A, 4B, and 4C. The introducer 120 illustrated in FIG. 4Ais a flat, planar, pointed strip of rigid material which may be attachedor otherwise coupled to the sensor 42 to ease insertion of the sensor 42into the skin of the patient, as well as to provide structural supportto the sensor 42 during insertion. The introducers 120 of FIGS. 4B and4C are U- or V-shaped implements that support the sensor 42 to limit theamount that the sensor 42 may bend or bow during insertion. Thecross-sectional width 124 of the introducers 120 illustrated in FIGS. 4Band 4C is typically 1 mm or less, preferably 700 μm or less, morepreferably 500 μm or less, and most preferably 300 μm or less. Thecross-sectional height 126 of the introducer 120 illustrated in FIGS. 4Band 4C is typically about 1 mm or less, preferably about 700 μm or less,and more preferably about 500 μm or less.

The sensor 42 itself may include optional features to facilitateinsertion. For example, the sensor 42 may be pointed at the tip 123 toease insertion, as illustrated in FIG. 3. In addition, the sensor 42 mayinclude a barb 125 which helps retain the sensor 42 in the subcutaneoustissue of the patient. The barb 125 may also assist in anchoring thesensor 42 within the subcutaneous tissue of the patient during operationof the sensor 42. However, the barb 125 is typically small enough thatlittle damage is caused to the subcutaneous tissue when the sensor 42 isremoved for replacement. The sensor 42 may also include a notch 127 thatcan be used in cooperation with a corresponding structure (not shown) inthe introducer to apply pressure against the sensor 42 during insertion,but disengage as the introducer 120 is removed. One example of such astructure in the insertion device is a rod (not shown) between twoopposing sides of an introducer 120 and at an appropriate height of theintroducer 120.

In operation, the sensor 42 is placed within or next to the introducer120 and then a force is provided against the introducer 120 and/orsensor 42 to carry the sensor 42 into the skin of the patient. In oneembodiment, the force is applied to the sensor 42 to push the sensorinto the skin, while the introducer 120 remains stationary and providesstructural support to the sensor 42. Alternatively, the force is appliedto the introducer 120 and optionally to the sensor 42 to push a portionof both the sensor 42 and the introducer 120 through the skin of thepatient and into the subcutaneous tissue. The introducer 120 isoptionally pulled out of the skin and subcutaneous tissue with thesensor 42 remaining in the subcutaneous tissue due to frictional forcesbetween the sensor 42 and the patient's tissue. If the sensor 42includes the optional barb 125, then this structure may also facilitatethe retention of the sensor 42 within the interstitial tissue as thebarb catches in the tissue.

The force applied to the introducer 120 and/or the sensor 42 may beapplied manually or mechanically. Preferably, the sensor 42 isreproducibly inserted through the skin of the patient. In oneembodiment, an insertion gun is used to insert the sensor. One exampleof an insertion gun 200 for inserting a sensor 42 is shown in FIG. 9.The insertion gun 200 includes a housing 202 and a carrier 204. Theintroducer 120 is typically mounted on the carrier 204 and the sensor 42is pre-loaded into the introducer 120. The carrier 204 drives the sensor42 and, optionally, the introducer 120 into the skin of the patientusing, for example, a cocked or wound spring, a burst of compressed gas,an electromagnet repelled by a second magnet, or the like, within theinsertion gun 200. In some instances, for example, when using a spring,the carrier 204 and introducer 120 may be moved, cocked, or otherwiseprepared to be directed towards the skin of the patient.

After the sensor 42 is inserted, the insertion gun 200 may contain amechanism which pulls the introducer 120 out of the skin of the patient.Such a mechanism may use a spring, electromagnet, or the like to removethe introducer 120.

The insertion gun may be reusable. The introducer 120 is oftendisposable to avoid the possibility of contamination. Alternatively, theintroducer 120 may be sterilized and reused. In addition, the introducer120 and/or the sensor 42 may be coated with an anticlotting agent toprevent fouling of the sensor 42.

In one embodiment, the sensor 42 is injected between 2 to 12 mm into theinterstitial tissue of the patient for subcutaneous implantation.Preferably, the sensor is injected 3 to 9 mm, and more preferably 5 to 7mm, into the interstitial tissue. Other embodiments of the invention,may include sensors implanted in other portions of the patient,including, for example, in an artery, vein, or organ. The depth ofimplantation varies depending on the desired implantation target.

Although the sensor 42 may be inserted anywhere in the body, it is oftendesirable that the insertion site be positioned so that the on-skinsensor control unit 44 can be concealed. In addition, it is oftendesirable that the insertion site be at a place on the body with a lowdensity of nerve endings to reduce the pain to the patient. Examples ofpreferred sites for insertion of the sensor 42 and positioning of theon-skin sensor control unit 44 include the abdomen, thigh, leg, upperarm, and shoulder.

An insertion angle is measured from the plane of the skin (i.e.,inserting the sensor perpendicular to the skin would be a 90° insertionangle). Insertion angles usually range from 10 to 90°, typically from 15to 60°, and often from 30 to 45°.

On-skin Sensor Control Unit

The on-skin sensor control unit 44 is configured to be placed on theskin of a patient. The on-skin sensor control unit 44 is optionallyformed in a shape that is comfortable to the patient and which maypermit concealment, for example, under a patient's clothing. The thigh,leg, upper arm, shoulder, or abdomen are convenient parts of thepatient's body for placement of the on-skin sensor control unit 44 tomaintain concealment. However, the on-skin sensor control unit 44 may bepositioned on other portions of the patient's body. One embodiment ofthe on-skin sensor control unit 44 has a thin, oval shape to enhanceconcealment, as illustrated in FIGS. 5-7. However, other shapes andsizes may be used.

The particular profile, as well as the height, width, length, weight,and volume of the on-skin sensor control unit 44 may vary and depends,at least in part, on the components and associated functions included inthe on-skin sensor control unit 44, as discussed below. For example, insome embodiments, the on-skin sensor control unit 44 has a height of 1.3cm or less, and preferably 0.7 cm or less. In some embodiments, theon-skin sensor control unit 44 has a weight of 90 grams or less,preferably 45 grams or less, and more preferably 25 grams or less. Insome embodiments, the on-skin sensor control unit 44 has a volume ofabout 15 cm³ or less, preferably about 10 cm³ or less, more preferablyabout 5 cm³ or less, and most preferably about 2.5 cm³ or less.

The on-skin sensor control unit 44 includes a housing 45, as illustratedin FIGS. 5-7. The housing 45 is typically formed as a single integralunit that rests on the skin of the patient. The housing 45 typicallycontains most or all of the electronic components, described below, ofthe on-skin sensor control unit 44. The on-skin sensor control unit 44usually includes no additional cables or wires to other electroniccomponents or other devices. If the housing includes two or more parts,then those parts typically fit together to form a single integral unit.

In some embodiments, conductive contacts 80 are provided on the exteriorof the housing 45. In other embodiments, the conductive contacts 80 areprovided on the interior of the housing 45, for example, within a hollowor recessed region.

In some embodiments, the housing 45 of the on-skin sensor control unit44 is a single piece. The conductive contacts 80 may be formed on theexterior of the housing 45 or on the interior of the housing 45 providedthere is a port 78 in the housing 45 through which the sensor 42 can bedirected to access the conductive contacts 80.

In other embodiments, the housing 45 of the on-skin sensor control unit44 is formed in at least two separate portions that fit together to formthe housing 45, for example, a base 74 and a cover 76, as illustrated inFIGS. 5-7. The two or more portions of the housing 45 may be entirelyseparate from each other. Alternatively, at least some of the two ormore portions of the housing 45 may be connected together, for example,by a hinge, to facilitate the coupling of the portions to form thehousing 45 of the on-skin sensor control unit 44.

These two or more separate portions of the housing 45 of the on-skinsensor control unit 44 may have complementary, interlocking structures,such as, for example, interlocking ridges or a ridge on one componentand a complementary groove on another component, so that the two or moreseparate components may be easily and/or firmly coupled together. Thismay be useful, particularly if the components are taken apart and fittogether occasionally, for example, when a battery or sensor 42 isreplaced. However, other fasteners may also be used to couple the two ormore components together, including, for example, screws, nuts andbolts, nails, staples, rivets, or the like. In addition, adhesives, bothpermanent or temporary, may be used including, for example, contactadhesives, pressure sensitive adhesives, glues, epoxies, adhesiveresins, and the like.

Typically, the housing 45 is at least water resistant to prevent theflow of fluids into contact with the components in the housing,including, for example, the conductive contacts 80. Preferably, thehousing is waterproof. In one embodiment, two or more components of thehousing 45, for example, the base 74 and the cover 76, fit togethertightly to form a hermetic, waterproof, or water resistant seal so thatfluids cannot flow into the interior of the on-skin sensor control unit44. This may be useful to avoid corrosion currents and/or degradation ofitems within the on-skin sensor control unit 44, such as the conductivecontacts, the battery, or the electronic components, particularly whenthe patient engages in such activities as showering, bathing, orswimming.

Water resistant, as used herein, means that there is no penetration ofwater through a water resistant seal or housing when immersed in waterat a depth of one meter at sea level. Waterproof, as used herein, meansthat there is no penetration of water through the waterproof seal orhousing when immersed in water at a depth of ten meters, and preferablyfifty meters, at sea level. It is often desirable that the electroniccircuitry, power supply (e.g., battery), and conductive contacts of theon-skin sensor control unit, as well as the contact pads of the sensor,are contained in a water resistant, and preferably, a waterproof,environment.

The on-skin sensor control unit 44 is typically attached to the skin 75of the patient, as illustrated in FIG. 8. The on-skin sensor controlunit 44 may be attached by a variety of techniques including, forexample, by adhering the on-skin sensor control unit 44 directly to theskin 75 of the patient with an adhesive provided on at least a portionof the housing 45 of the on-skin sensor control unit 44 which contactsthe skin 75, by suturing the on-skin sensor control unit 44 to the skin75 through suture openings (not shown) in the sensor control unit 44, orby strapping the on-skin sensor control unit 44 to the skin 75.

Another method of attaching the housing 45 of the on-skin sensor controlunit 44 to the skin 75 includes using a mounting unit, 77. The mountingunit 77 is often a part of the on-skin sensor control unit 44. Oneexample of a suitable mounting unit 77 is a double-sided adhesive strip,one side of which is adhered to a surface of the skin of the patient andthe other side is adhered to the on-skin sensor control unit 44. In thisembodiment, the mounting unit 77 may have an optional opening 79 whichis large enough to allow insertion of the sensor 42 through the opening79. Alternatively, the sensor may be inserted through a thin adhesiveand into the skin.

A variety of adhesives may be used to adhere the on-skin sensor controlunit 44 to the skin 75 of the patient, either directly or using themounting unit 77, including, for example, pressure sensitive adhesives(PSA) or contact adhesives. Preferably, an adhesive is chosen which isnot irritating to all or a majority of patients for at least the periodof time that a particular sensor 42 is implanted in the patient.Alternatively, a second adhesive or other skin-protecting compound maybe included with the mounting unit so that a patient, whose skin isirritated by the adhesive on the mounting unit 77, can cover his skinwith the second adhesive or other skin-protecting compound and thenplace the mounting unit 77 over the second adhesive or otherskin-protecting compound. This should substantially prevent theirritation of the skin of the patient because the adhesive on themounting unit 77 is no longer in contact with the skin, but is insteadin contact with the second adhesive or other skin-protecting compound.

Returning to FIG. 8, when the sensor 42 is changed, the on-skin sensorcontrol unit 44 may be moved to a different position on the skin 75 ofthe patient, for example, to avoid excessive irritation. Alternatively,the on-skin sensor control unit 44 may remain at the same place on theskin of the patient until it is determined that the unit 44 should bemoved.

Another embodiment of a mounting unit 77 used in an on-skin sensorcontrol unit 44 is illustrated in FIGS. 10A and 10B. The mounting unit77 and a housing 45 of an on-skin sensor control unit 44 are mountedtogether in, for example, an interlocking manner, as shown in FIG. 10A.The mounting unit 77 is formed, for example, using plastic or polymermaterials, including, for example, polyvinyl chloride, polyethylene,polypropylene, polystyrene, ABS polymers, and copolymers thereof. Themounting unit 77 may be formed using a variety of techniques including,for example, injection molding, compression molding, casting, and othermolding methods.

The mounting unit 77 typically includes an adhesive on a bottom surfaceof the mounting unit 77 to adhere to the skin of the patient or themounting unit 77 is used in conjunction with, for example, double-sidedadhesive tape or the like. The mounting unit 77 typically includes anopening 79 through which the sensor 42 is inserted, as shown in FIG.10B. The mounting unit 77 may also include a support structure 220 forholding the sensor 42 in place and against the conductive contacts 80 onthe on-skin sensor control unit 42. The mounting unit 77, also,optionally, includes a positioning structure 222, such as an extensionof material from the mounting unit 77, that corresponds to a structure(not shown), such as an opening, on the sensor 42 to facilitate properpositioning of the sensor 42, for example, by aligning the twocomplementary structures.

In another embodiment, a coupled mounting unit 77 and housing 45 of anon-skin sensor control unit 44 is provided on an adhesive patch 204 withan optional cover 206 to protect and/or confine the housing 45 of theon-skin sensor control unit 44, as illustrated in FIG. 11A. The optionalcover may contain an adhesive or other mechanism for attachment to thehousing 45 and/or mounting unit 77. The mounting unit 77 typicallyincludes an opening 49 through which a sensor 42 is disposed, as shownin FIG. 11B. The opening 49 may optionally be configured to allowinsertion of the sensor 42 through the opening 49 using an introducer120 or insertion gun 200 (see FIG. 9). The housing 45 of the on-skinsensor control unit 44 has a base 74 and a cover 76, as illustrated inFIG. 11C. A bottom view of the housing 45, as shown in FIG. 11D,illustrates ports 230 through which conductive contacts (not shown)extend to connect with contact pads on the sensor 42. A board 232 forattachment of circuit components may optionally be provided within theon-skin sensor control unit 44, as illustrated in FIG. 11E.

In some embodiments, the adhesive on the on-skin sensor control unit 44and/or on any of the embodiments of the mounting unit 77 is waterresistant or waterproof to permit activities such as showering and/orbathing while maintaining adherence of the on-skin sensor control unit44 to the skin 75 of the patient and, at least in some embodiments,preventing water from penetrating into the sensor control unit 44. Theuse of a water resistant or waterproof adhesive combined with a waterresistant or waterproof housing 45 protects the components in the sensorcontrol unit 44 and the contact between the conductive contacts 80 andthe sensor 42 from damage or corrosion. An example of a non-irritatingadhesive that repels water is Tegaderm™ (3M™, St. Paul, Minn.).

In one embodiment, the on-skin sensor control unit 44 includes a sensorport 78 through which the sensor 42 enters the subcutaneous tissue ofthe patient, as shown in FIGS. 5 to 7. The sensor 42 may be insertedinto the subcutaneous tissue of the patient through the sensor port 78.The on-skin sensor control unit 44 may then be placed on the skin of thepatient with the sensor 42 being threaded through the sensor port 78. Ifthe housing 45 of the sensor 42 has, for example, a base 74 and a cover76, then the cover 76 may be removed to allow the patient to guide thesensor 42 into the proper position for contact with the conductivecontacts 80.

Alternatively, if the conductive contacts 80 are within the housing 45the patient may slide the sensor 42 into the housing 45 until contact ismade between the contact pads 49 and the conductive contacts 80. Thesensor control unit 44 may have a structure which obstructs the slidingof the sensor 42 further into the housing once the sensor 42 is properlypositioned with the contact pads 49 in contact with the conductivecontacts 80.

In other embodiments, the conductive contacts 80 are on the exterior ofthe housing 45 (see e.g., FIGS. 10A-10B and 11A-11E). In theseembodiments, the patient guides the contact pads 49 of the sensor 42into contact with the conductive contacts 80. In some cases, a guidingstructure may be provided on the housing 45 which guides the sensor 42into the proper position. An example of such a structure includes a setof guiding rails extending from the housing 45 and having the shape ofthe sensor 42.

In some embodiments, when the sensor 42 is inserted using an introducer120 (see FIG. 3), the tip of the introducer 120 or optional insertiongun 200 (see FIG. 9) is positioned against the skin or the mounting unit77 at the desired insertion point. In some embodiments, the introducer120 is positioned on the skin without any guide. In other embodiments,the introducer 120 or insertion gun 200 is positioned using guides (notshown) in the mounting unit 77 or other portion of the on-skin sensorcontrol unit 44. In some embodiments, the guides, opening 79 in themounting unit 77 and/or sensor port 78 in the housing 45 of the on-skinsensor control unit 44 have a shape which is complementary to the shapeof the tip of the introducer 120 and/or insertion gun 200 to limit theorientation of the introducer 120 and/or insertion gun 200 relative tothe opening 79 and/or sensor port 78. The sensor can then besubcutaneously inserted into the patient by matching the complementaryshape of the opening 79 or sensor port 78 with the introducer 120 and/orinsertion gun 200.

In some embodiments, the shapes of a) the guides, opening 79, or sensorport 78, and (b) the introducer 120 or insertion gun 200 are configuredsuch that the two shapes can only be matched in a single orientation.This aids in inserting the sensor 42 in the same orientation each time anew sensor is inserted into the patient. This uniformity in insertionorientation may be required in some embodiments to ensure that thecontact pads 49 on the sensor 42 are correctly aligned with appropriateconductive contacts 80 on the on-skin sensor control unit 44. Inaddition, the use of the insertion gun, as described above, may ensurethat the sensor 42 is inserted at a uniform, reproducible depth.

An exemplary on-skin sensor control unit 44 can be prepared and used inthe following manner. A mounting unit 77 having adhesive on the bottomis applied to the skin. An insertion gun 200 (see FIG. 9) carrying thesensor 42 and the introducer 120 is positioned against the mounting unit77. The insertion gun 200 and mounting unit 77 are optionally designedsuch that there is only one position in which the two properly mate. Theinsertion gun 200 is activated and a portion of the sensor 42 andoptionally a portion of the introducer 120 are driven through the skininto, for example, the subcutaneous tissue. The insertion gun 200withdraws the introducer 120, leaving the portion of the sensor 42inserted through the skin. The housing 45 of the on-skin control unit 44is then coupled to the mounting unit 77. Optionally, the housing 45 andthe mounting unit 77 are formed such that there is only one position inwhich the two properly mate. The mating of the housing 45 and themounting unit 77 establishes contact between the contact pads 49 (seee.g., FIG. 2) on the sensor 42 and the conductive contacts 80 on theon-skin sensor control unit 44. Optionally, this action activates theon-skin sensor control unit 44 to begin operation.

The introducer, sensor, insertion gun and mounting unit can bemanufactured, marketed, or sold as a unit. For example, FIG. 12 depictsan introducer 270, sensor 272, insertion gun 274 and mounting unit 276,which can be assembled (as indicated by the arrows) and sold together inan insertion kit. In such an embodiment of an insertion kit, theinsertion gun 274 can be packaged in a pre-loaded fashion, with anintroducer 270 and sensor 272 mated or otherwise coupled, the matedsensor 272 and introducer 270 loaded upon the carrier 278 of theinsertion gun, and with a mounting unit 276 already mated with the endof the insertion gun 274.

In one embodiment, the insertion gun 274 is packaged in a state where itis ready to thrust the sensor 272 (and perhaps introducer 270) intosubcutaneous tissue. For example, the insertion gun 274 can be packagedin a “cocked” state, such that the thrusting force used to introduce thesensor 272 into the subcutaneous tissue is stored in the device aspotential energy (in the case of the embodiment depicted in FIG. 12, theinsertion gun 274 would be “cocked” by compressing its spring 280, thusstoring potential energy within the coils of the spring). Preferably, aninsertion gun 274 packaged in such a manner employs a “safety”, abarrier to prevent the release of the stored potential energy. Thebarrier is removed in order to permit the potential energy to bereleased. Within the context of the embodiment presented in FIG. 12, anexample of a safety is a pin (not pictured) that impedes the spring fromexpanding, once compressed. Thus, an insertion kit so embodied can beobtained at a place of purchase, removed from its package, and usedafter removal of the safety, without necessitating additional steps.Alternatively, the insertion gun 274 can be packaged in theabove-described pre-loaded configuration, but without being “cocked”.Thus, an insertion kit with an “uncocked” insertion gun 274 can beobtained at a place of purchase, removed from its package, cocked, andused. To facilitate the insertion kit being ready to use with minimaluser-exercised steps, the insertion kit can be sterilized prior topackaging. Examples of acceptable sterilizing techniques includeexposing the elements of the insertion kit to gamma radiation or ane-beam.

Referring to FIGS. 13-33B, preferred commercial embodiments of a sensorinserter constructed according to the invention will now be described.FIG. 13 shows an overall perspective view of a sensor inserter kit 300comprising a single-use sensor inserter 310 and a single-use adhesivemount 312 removably attached to the bottom thereof.

As an overview of the operation of inserter kit 300, the kit comespackaged generally as shown in FIG. 13 with a sensor 314 (best seen inFIGS. 16 and 25) preloaded within inserter 310 and with inserter 310 ina “cocked” state. After preparing an insertion site on the skin,typically in the abdominal region, the patient removes upper liner 316and lower liner 318 from adhesive mount 312 to expose the bottom surfaceand a portion of the top surface of an adhesive tape 320 (best seen inFIG. 16) located beneath mount 312. Mount 312, with inserter 310attached, is then applied to the patient's skin at the insertion site.Safety lock tabs 322 are squeezed together to allow actuator button 324to be pressed causing inserter 310 to fire, thereby inserting sensor 314into the patient's skin with a predetermined velocity and force. Oncesensor 314 has been inserted into the skin, the patient removes inserter310 from mount 312 by pressing release tabs 326 on opposite sides ofinserter 310 and lifting inserter 310 away from mount 312.

Referring to FIG. 14, mount 312 is shown adhered to a patient's skin 328with sensor 314 already inserted. Once inserter 310 is removed frommount 312, transmitter 330 can be slid into place. The circuitry oftransmitter 330 makes electrical contact with the contact pads on sensor314 after transmitter 330 is fully seated on mount 312. Onceinitialization and synchronization procedures are completed,electrochemical measurements from sensor 314 can be sent wirelessly fromtransmitter 330 to a portable receiver 332, as shown in FIG. 15. Sensor314, mount 312 and transmitter 330 remain in place on the patient for apredetermined period, currently envisioned to be three days. Thesecomponents are then removed so that sensor 314 and mount 312 can beproperly discarded. The entire procedure above can then be repeated witha new inserter 310, sensor 314 and mount 312, reusing transmitter 330and receiver 332.

Referring to FIG. 16, the preferred inserter kit 300 is assembled asshown from the following components: housing 334, actuator button 324,drive spring 336, shuttle 338, introducer sharp 340, sensor 314,retraction spring 342, inserter base 344, upper liner 316, adhesivemount 312, adhesive tape 320, and lower liner 318.

Sensor 314 has a main surface 346 slidably mounted between U-shapedrails 348 of introducer sharp 340 and releasably retained there bysensor dimple 350 which engages introducer dimple 352. Introducer sharp340 is mounted to face 354 of shuttle 338, such as with adhesive, heatstake or ultrasonic weld. Sensor 314 also has a surface 356 that extendsorthogonally from main surface 346 and just beneath a driving surface358 of shuttle 338 when mounted thereon (details of these features arebetter shown in FIGS. 19 and 25-27.)

Shuttle 338 is slidably and non-rotatably constrained on base 344 byarcuate guides 360. As best seen in FIGS. 19, 24 and 27, shuttle 338 isgenerally formed by an outer ring 362 and an inner cup-shaped post 364connected by two bridges 366. Bridges 366 slide between the two slots368 formed between guides 360 and allow shuttle 338 to travel alongguides 360 without rotating. Retraction spring 342 is captivated at itsouter circumference by guides 360, at its bottom by the floor 370 ofbase 344, at its top by bridges 366, and at its inner circumference bythe outer surface of shuttle post 364. Drive spring 336 is captivated atits bottom and outer circumference by the inside surface of shuttle post364, at its top by the ceiling 372 inside actuator button 324, and atits inner circumference by stem 374 depending from ceiling 372. Whendrive spring 336 is compressed between actuator button 324 and shuttle338 it urges shuttle 338 towards base 344. When retraction spring 342 iscompressed between shuttle 338 and base 344, it urges shuttle 338towards actuator button 324.

Actuator button 324 is slidably received within housing 334 from belowand resides in opening 376 at the top of housing 334 with limitedlongitudinal movement. Arms 378 on each side of actuator button 324travel in channels 380 along the inside walls of housing 334, as bestseen in FIG. 20. Longitudinal movement of actuator button 324 is limitedin one direction by the base of arms 378 contacting the edge of opening376 at the top of housing 334, and in the other direction by the distalends 384 of arms 378 contacting stops 386 in channels 380. Slots 388 arepreferably provided in the top of housing 334 for ease of housingmanufacture and so tools can be inserted to inwardly compress arms 378beyond stops 386 to allow actuator button 324 to be removed from housing334 if needed.

When sensor 314, introducer sharp 340, shuttle 338, retraction spring342, drive spring 336 and actuator button 324 are assembled between base344 and housing 334 as shown in FIG. 16 and described above, housing 334is snapped into place on base 344. Base 344 is held onto housing 334 byupper base barbs 390 that engage upper openings 392 in housing 334, andlower base barbs 394 (best seen in FIG. 17) that engage lower openings396 in housing 334. Slots 398 and 400 are provided for ease ofmanufacture of housing 334, and base 344 is preferably removable fromhousing 334 with tools if needed.

Referring to FIG. 19, actuator button 324 is preferably provided withsafety lock tabs 322 hingedly formed on opposite ends. Tabs 322 can beurged from a relaxed outward position to a flexed inward position. Whenin the normal outward position, shoulders 402 on the outer surfaces oftabs 322 engage the rim 404 of opening 376 to prevent the actuatorbutton 324 from being depressed, thereby avoiding accidental firing ofinserter 310. Tabs 322 can be squeezed inward just enough to clear therim 404 of opening 376 while pressing the actuator button 324 down tofire the inserter. Alternatively, tabs 322 can be squeezed furtherinward so that barbs 406 on the inside edges can engage catches 408located on a center portion of actuator button 324, thereby defeatingthe safety lock to allow later firing by simply pressing down on theactuator button 324. Preferably, upwardly extending grips are providedon tabs 322 for better visual indication of safety lock status andactuation control.

Referring to FIG. 20, shuttle 338 is provided with laterally extendingbarbed fingers 412 which travel in channels 380 along the inside wallsof housing 334. When shuttle 338 is inserted up into housing 334 farenough, barbed fingers 412 momentarily deflect inward and then snapoutward again to catch on stops 386. In this “cocked” position as shown,drive spring 336 is compressed and urging shuttle 338 towards base 344,but barbed fingers 412 catching on stops 386 prevent such travel.

Referring to FIGS. 21-23, the sequence of loading, cocking, arming,firing, and automatic retraction of inserter 310 will be described. Itis envisioned that in production, inserters 310 will be fabricated andfully assembled by one vender except for sensor 314, which will besupplied and installed by a second vendor in a sterile environment.Accordingly, inserter 310 will be manufactured and shipped to the sensorvendor in a neutral state, as shown in FIG. 21. A hole 414 providedthrough the center of actuator button 324 allows the sensor vendor toinsert a pin (manually or by automated machinery, not shown) throughhole 414 to drive shuttle 338 towards base 344 in a controlled fashionand hold it there against the force of retraction spring 342. This willcause introducer sharp 340 to be extended through base 344 (as shown inFIG. 23) so that sensor 314 can be loaded into introducer 340. When thepin is removed, shuttle 338, introducer 340 and sensor 314 will retractto the neutral position. The sensor vendor can then cock the loadedinserter 310 before shipment by pushing another pin (not shown) from theopposite direction through a central hole 416 in base 344 (with mount312 removed) until the pin contacts dimple 418 formed in the bottom ofshuttle 338. By pushing shuttle 338 towards actuator button 324 untilbarbed fingers 412 clear stops 386, the inserter 310 is cocked (as shownin FIG. 22.)

Referring to FIG. 22, inserter 310 is preferably received by the patientin the cocked position as shown. To use inserter 310, the patientapplies mount 312 to the mounting site and disables the safety mechanismas previously described, and then pushes actuator button 324 against theforce of drive spring 336. As actuator button 324 travels toward base344, drive cam surfaces 420 on arms 378 contact ramped surfaces 422 ofbarbed fingers 412 and urge them inward. When fingers 412 are driveninward enough to clear stops 386, shuttle 338 is driven by drive spring336 with a predetermined speed and force to an insertion position, asshown in FIG. 23.

Referring to FIG. 23, inserter 310 is shown in the insertion positionwith the tail 424 of introducer sharp 340 extending through base 344 andmount 312 into the skin of the patient. FIG. 23 shows shuttle 338 in afully extended position with its lower surface 426 bottomed out on base344. However, the lower orthogonal surface 356 of sensor 314 willcontact an exposed sensor contact portion 428 (best seen in FIG. 16) ontop of adhesive tape 320 supported from below by the patient's skin, andtherefore will typically stop traveling before reaching the fullybottomed out position shown. Tail 424 of introducer sharp 340 providesrigidity and a skin piercing edge 430 for allowing the flexible tail 431of sensor 314 to be implanted in the patient's skin. After providingthis function, introducer sharp 340 is immediately removed from thepatient and retracted into a safe position inside housing 334 asrefraction spring 342 (which has been compressed by the travel of theshuttle) pushes shuttle 338 back towards actuator cap. Sensor 314 ispulled from introducer sharp 340 and held in place by the sensor contactportion 428 on top of adhesive tape 320 adhering to orthogonal surface356 of sensor 314. The geometries of sensor dimple 350 and matingintroducer dimple 352 are chosen to create a separation force betweenthem that is less than the adhesion force of tape 320 on orthogonalsurface 356, but great enough to retain sensor 314 in introducer sharp340 during typical shipping and product handling shock loads. Drivingsurface 358 beneath shuttle 338 presses down on top of orthogonalsurface 356 to ensure good contact with adhesive tape 320 before shuttle338 retracts with introducer sharp 340. As discussed above with previousembodiments, barb(s) on sensor tail 431 can be employed to furtheranchor the sensor in its operating position.

Referring again to FIG. 21, retraction spring 342 will return shuttle338 to the neutral position as shown after firing, but without sensor314 which remains inserted in patient's skin (not still in introducersharp 340 as shown). Drive spring 336 is preferably designed to bestiffer than retraction spring 342 so that shuttle 338 oscillations arequickly dampened out, and so introducer sharp 340 does not return tosensor 314 or the patient to cause injury. With sensor 314 now insertedin the patient's skin, inserter 310 can be removed from mount 312 byinwardly flexing release tabs 326 on opposite sides of inserter 310 toremove latch hooks 432 from mount channels 434 and then lifting inserter310 away from mount 312. Introducer sharp 340 remains protected insidehousing 334 during disposal of inserter 310. Transmitter 330 can now beslid into place on mount 312 as previously described.

Referring to FIG. 28, an alternative embodiment of adhesive tape 320′ isshown. This oversized tape 320′ has the advantage of holding transmitter330 in place even when fairly large forces are placed on it. In thisembodiment adhesive tape 320′ has a double-sided portion 436 (adhesiveon both top and bottom sides) residing between mount 312 and thepatient's skin, and a single-sided portion 438 outwardly extending fromthe double-sided portion 436, preferably in all directions, for adheringjust to the patient's skin. In the previous embodiment, it is difficultto separate mount 312 from the skin merely with tension forces, butapplying a force to just one side of mount 312 results in a high peelingforce being applied to that edge of the adhesive tape 320 which causestape 320 to peel off of the skin. In contrast, any force applied totransmitter 330 in this alternative embodiment results in a tensionforce rather than a peeling force being applied to tape 320′, inhibitinginadvertent removal until an edge of tape 320′ is intentionally peeledup. Preferably, single-sided portion 438 has a width roughly double thewidth of double-sided portion 436. In the preferred embodiment, theseswidths are 2.14 and 1.14 inches, respectively. Preferably, the lengththat single-sided portion 438 extends beyond double-sided portion 436 isroughly equivalent to the combined height of transmitter 330 attached tomount 312, in this case about 0.5 inches.

In the preferred embodiment, sensor 314 is made from a 0.005 inch thickMylar® substrate, such as Dupont Melinex ST-505, print treated bothsides, heat stabilized and bi-axially oriented. Main surface 346 is0.315 tall by 0.512 wide, and orthogonal surface 356 is 0.374 wide by0.202 deep. Sensor tail 431 is 0.230 long by 0.023 wide. Semisphericalsensor dimple 350 is 0.050 inches wide and 0.026 inches deep. Introducersharp 340 is made from SUS 301 medical grade stainless steel, 0.004inches thick, having a surface roughness less than or equal to 0.5micrometers. The height of the main portion of introducer sharp 340 is0.614 inches, and the inside width is 0.513 inches. The overallthickness of rolled rails 348 is 0.026 inches. The length and width ofintroducer tail 424 are 0.354 and 0.036 inches, respectively. Thepreferred angle of the introducer sharp 340 is 21 degrees. Preferably,semispherical introducer dimple 352 has a radius of 0.024 inches. In thepreferred embodiment, shuttle 338 has an average speed of at least 1meter/second, and has a momentum at its end of travel of about 2.65lb-m/sec.

Preferably, housing 334, button 324, shuttle 338, base 344 and mount 312are all injection molded from G.E. Lexan PC. Inside and outside workingsurfaces of arms 378 on button 324 are preferably lubricated with DowCorning 360 Medical Fluid. Drive spring 336 has a free length of 1.25inches, a working length of 1.00 inch, and a rate between 20 and 30pounds per inch. Retraction spring 342 has a free length of 1.5 inches,a working length of 0.35 inches, and a rate between 0.15 and 0.35 poundsper inch. Adhesive tape 320 preferably is medical grade acrylic adhesiveon polyester film (such as Acutek 0396013) with a semi-bleached kraftliner having silicon release.

Referring to FIG. 29, an interconnect 440 is shown for providingwaterproof electrical connections between sensor 314 and transmitter330. Interconnect 440 includes a seal 442 mounted on an end oftransmitter 330 that contacts one side of sensor 314 when transmitter330 is slid onto mount 312. When transmitter 330 is locked into place onmount 312, seal 442 is compressed between transmitter 330 and sensor 314and urges sensor 314 against raised end stop 444 of mount 312.

Referring to FIG. 30, further details of interconnect 440 are shown.Seal 442 has an exterior wall 446 for surrounding electrical contacts448 (in this case four), and interior walls 450 for isolating electricalcontacts 448 from each other. Rim 452 formed on the transmitter housing330 surrounds the base 454 of seal 442 to prevent it from collapsingoutward when compressed (see FIGS. 31-32).

Referring to FIG. 31, an enlarged partial view of FIG. 30 is shown withseal 442 and one spring removed for clarity. Electrical contacts 448 arepreferably constructed from compression springs 456 mounted on connectorlugs 458. Lugs 458 are stamped rearward on their edges to formprotrusions that retain springs 456. Alternately or in conjunction withthis stamping, plastic rings (not shown) can be melted over the base ofeach spring 456 for attaching it to its respective lug 458. Connectorlugs 458 can protrude through slots in transmitter 330, or be insertmolded integral with the plastic housing when it is molded.

Referring to FIG. 32, an enlarged perspective view of the seal 442 isshown. It has been discovered through experimentation that two lips 462of equal height along the distal edge of exterior wall 446 provide thebest seal from exterior elements. Good isolation between electricalcontacts 448 is best achieved by having interior walls 450 with a heightequal to that of lips 462. Recesses 464 should be sized large enough sothat seal 442 does not interfere with the movement of springs 456 whenseal 442 and springs 456 are compressed. In the preferred embodiment,the distal face of seal 442 defined by lips 462 is formed at a 1 degreeangle to match the draft angle of mount end stop 444.

Seal 442 is preferably made of shore A 30 durometer compression moldedsilicone. It is envisioned that seal 442 can be shortened in the axialdirection (parallel to springs 456) to reduce the force required tocompress it when attaching transmitter 330 to mount 312. Best resultsfor fastening seal 442 to transmitter 330 have been achieved with doublesided adhesive tape 320, silicone adhesive on one side and acrylicadhesive on the other for sticking to the PC-ABS blend of thetransmitter 330, such as product number 9731 manufactured by 3M Companyof St. Paul, Minn. Springs 456 are preferably made from gold-platedberyllium copper so as to deter galvanic current effects. Preferably,main surface 346 of sensor 314 that contacts seal 442 has a uniformthickness dielectric coating with a window in it (i.e. no dielectric)where springs 456 contact sensor 314. An interconnect 440 constructed asdescribed above remains water proof when submerged to a depth of atleast 1 meter for 45 minutes.

To increase the reliability of sensor insertion, the followingenhancements can be added to the inserter kit 300 described above.First, a sensor flap can be formed along the top edge of sensor 314.When sensor 314 reaches the extended, delivered position as shown inFIG. 23, the flap catches on the bottom edge of base 344 to ensure thatsensor 314 separates from introducer sharp 340 as shuttle 338 returnsupward to the retracted position. Adhesive can also be located on thebottom of orthogonal sensor surface 356 to ensure that sensor 314adheres to the sensor contact portion 428 on the top of adhesive mounttape 320, as shown in FIG. 16.

Referring to FIGS. 33A and 33B, actuator button 324′ can be made easierfor elderly patients to push by anchoring the upper end of drive spring336 on a housing bridge 470 instead of button 324. This change alsomakes the insertion force of inserter 310 more consistent, and allowsstronger spring forces to be used if desired. Bridge 470 spans acrossopening 376′ and divides it into two openings 472 in the top of housing334′. The top portion of button 324′ is bifurcated into two protrusions474 that each extend through an opening 472. A clearance hole (notshown) is provided through the center of button 324′ to allow drivespring 336 to pass through and secure around a post (not shown)depending from the bottom center of bridge 470.

Safety lock key 476 can be provided to prevent actuator button 324′ frombeing pressed until key 476 is removed. Aperture 478 is provided in thetop center of bridge 470 for receiving boss 480 located at the bottom ofkey 476, thereby allowing key 476 to rotate. When key handle 482 isrotated perpendicular to button protrusions 474 as shown, two opposingperpendicular fins 484 on key 476 swing into inwardly facing slots (notshown) on the inside of protrusions 474 and prevent button 324′ frombeing actuated. When key handle 482 and fins 484 are rotated parallel tobutton protrusions 474 such that fins 484 disengage therefrom, key 476can be removed and button 324′ can then be actuated. Other than thesemodifications, this inserter kit 300′ functions the same as theembodiment previously described.

To provide an easier and more consistent release of shuttle 338 byactuator button 324 or 324′, it is envisioned that less aggressivefinger engagement with stops 386 can be employed, or the above designscan be modified to have a single, more centrally located shuttle releasefinger (not shown) instead of the two outboard fingers 412 shown.

The present invention should not be considered limited to the particularexamples described above. Various modifications, equivalent processes,as well as numerous structures to which the present invention may beapplicable and which fall within the general scope of the invention willbe readily apparent to those of skill in the art to which the presentinvention is directed upon review of the instant specification.

What is claimed is:
 1. An assembly, comprising: a mount configured forpositioning on a skin surface; a sensor comprising a proximal portionand a distal portion, wherein the distal portion of the sensor isconfigured to be transcutaneously positioned in contact withinterstitial fluid; an introducer configured to engage with the sensorduring transcutaneous positioning of the sensor and comprising aproximal portion and a distal portion, wherein the distal portion isconfigured to pierce through the skin surface; and a sensor inserterhousing configured to be detachably coupleable to the mount to form asensor insertion assembly; wherein the sensor inserter housing isconfigured to decouple from the mount when opposing forces are appliedto engaging members on opposing sides of the sensor insertion assembly.2. The assembly of claim 1, wherein the sensor inserter housing isconfigured to decouple from the mount after the distal portion of thesensor is transcutaneously positioned under the skin surface in contactwith the interstitial fluid.
 3. The assembly of claim 1, furthercomprising an actuator coupled to the introducer and configured to movethe sensor and introducer in an insertion direction to an extendedposition in which at least a portion of the introducer and the sensorprotrude from the housing to pierce through the skin surface prior toreaching the extended position.
 4. The assembly of claim 3, wherein aposition of the mount is configured to be fixed relative to the sensorinserter housing when the introducer and the sensor move in theinsertion direction to the extended position.
 5. The assembly of claim4, wherein the sensor is configured to be released from the introducerwhen the introducer moves in a retraction direction from the extendedposition to a retracted position.
 6. The assembly of claim 5, whereinthe introducer is configured to be retained entirely within the sensorinserter housing and physically separated from the sensor when in theretracted position.
 7. The assembly of claim 3, wherein the actuatorincludes a manual actuator configured to apply a manual force to movethe introducer in the insertion direction.
 8. The assembly of claim 5,wherein the sensor inserter housing is configured to decouple from themount when the introducer is at the retracted position within thehousing and separated from the sensor.
 9. The assembly of claim 5,wherein the actuator is axially aligned with the sensor and theintroducer along the insertion and retraction directions.
 10. Theassembly of claim 3, wherein the mount is configured for positioning onthe skin surface prior to moving the sensor and the introducer to theextended position.
 11. The assembly of claim 3, wherein the mount iscoupled to the sensor inserter housing prior to moving the sensor andthe introducer to the extended position.
 12. The assembly of claim 1,wherein the sensor insertion assembly includes one or more latch hooksof the sensor inserter housing coupled to one or more latch hooks of themount.
 13. The assembly of claim 12, wherein one or more release tabs ofthe sensor inserter housing are configured to inwardly flex when theopposing forces are applied to the engaging members of the sensorinsertion assembly.
 14. The assembly of claim 13, wherein the one ormore latch hooks of the mount are configured to decouple from the one ormore latch hooks of the sensor inserter housing when the opposing forcesare applied to the engaging members of the sensor insertion assembly.15. The assembly of claim 1, wherein the introducer is configured toslidably receive the sensor therein.
 16. The assembly of claim 1,wherein the distal portion of the introducer defines a skin-piercingedge.
 17. The assembly of claim 1, wherein the introducer comprisesstainless steel.
 18. The assembly of claim 1, wherein the mount isconfigured to remain positioned on the skin surface after the sensorinserter housing is decoupled from the mount.
 19. The assembly of claim1, wherein the mount includes an adhesive layer configured to adhere tothe skin surface.
 20. The assembly of claim 3, further including asafety mechanism configured for detachably coupling to the actuatorprior to moving the sensor and introducer in the insertion direction tothe extended position.